Honda CG125 crankshaft

[carofmadness]

This is my first post here and I have been riding a few years now but I have recently been rebuild my first bike a 1985 CG125, the only reason I stopped riding it was because it got stolen.

I now have a 2018 Royal Enfield Continental GT 535 single cylinder as my daily that I have had from new but would like my CG to use through the winter to keep my enfield nice and pretty so . . . .

I am making this into the small cafe racer that I desired as a teenager but I am having an issue with a knocking sound from the generator cover casing, upon closer inspection the woodruff key and the slot it goes into on the crankshaft are damaged and there is also some play in the con rod bearing.

I have been looking for a new crank but I am unable to find a part number for that year of bike (checked direct from honda) and lots of Chinese copies come up but I dont know if they will fit.

so does anyone know if a Chinese crankshaft will fit / know the part number of the crankshaft that is used? does anyone also know if there are any differences the crankshafts used on these bikes as I know there are many variations of this bike ie could i use a crank from a 1995 in my 1985?

any and all help would be appreciated.

I will post some pictures when I get a chance

[Riejufixing]

There seem to be several different CG125s for that year (E, F, BRE, BRF...); which is yours (perhaps it's stamped on th crankcase somewhere)?

[carofmadness]

I believe it is a it says brf on the log book bit the engine case says BRE
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2018 Black Royal Enfield Continental GT 535 Single Cylinder (daily) : 1985 Honda CG125 (my first bike) : 2014 AJS Daytona 125 (my mums bike)

[stinkwheel]

Try: 13000397010 ?

It would almost certainly be cheaper to get another engine than a new Honda crank. Assuming it's the above, they come in at £838.

Cranks can usually be repaired. Got any pictures of the damage?

The play on the big end? Vertical or horizontal? Vertical play is a no-no but they are needle rollers and push-fit crank pins, these can be replaced. A certain amount of horizontal play is ok. You can buy conrod kits for CG125s quite inexpensively (new rod, new big end bearing and crankpin).

The key is just for locating the flywheel on the crank, it's the taper that holds it. If you get it on in exactly the correct place, you could miss the key out providing the taper is good. It would take a lot of damage to render the slot totally unuseable though and even then, it could probably be machined to accept a larger key. You can also lap the flywheel onto the taper with grinding paste for a really good fit if there is a moderate amount of damage.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Riejufixing]

Yes. Might be a good idea to get the thing reconditioned. New big end, con rod, crankpin, bearings. Might be a ton, though.

[carofmadness]

When the bike was stolen it was partially stripped meaning the flywheel and cover were removed for some time and the taper has corrosion and the keyway is damaged, the key moves 1.5mm either way. The cost for me is not an issue as I don't see myself getting rid of the bike for a long time, it has sat in my garage for 4 years so it's not going anywhere.

I think it would be best to recon the crank just for peace of mind, the Conrod bearing has play horizontally and it is more than I would expect.

Any recommendations for a good place to get a crank reconditioned? The taper and keyway will need repair, it's not too bad but bad enough to not be nice and smooth. I'm going down my garage tomorrow morning so I will take some pictures then.

Thanks for all of your input
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2018 Black Royal Enfield Continental GT 535 Single Cylinder (daily) : 1985 Honda CG125 (my first bike) : 2014 AJS Daytona 125 (my mums bike)

[Riejufixing]

Hm, tricky. There are a couple of people advertising a reconditioning service on eBay (Honda CG 125 crank recondition), items 264605065664 and 303359965085, £87 to £150, and also https://predatormotorsport.co.uk/HONDA-CG125-MODELS-UP-TO-J-CRANK-RECONDITIONED-EXCHANGE-UNIT/ £103 + extra for damaged keyway, BUT I have no idea whether any of them are any good.

[stinkwheel]

Alpha bearings are generally the goto for a crank rebuild. Their website is shocking, give them a phone/email. They can almost certainly broach a keyway too which I'd imagine would be beyond many crank builders.

In fairness, you'll probably find a lot of the places offering recon cranks are actually subbing them out to alpha anyway.

Next question, do you want to bore and stroke it while you're in there?...There are commercially available 150cc barrels...
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Riejufixing]

[carofmadness]

No point boring to a 150, due 5o it being a Brazilian engine the crankcase will also need machining to fit a larger bore and for the gains it will get it's just not worth the money.

My commute is only 10 miles and I still get 70 out of the old girl. It already has free flowing exhaust, pod filter and a rejet
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2018 Black Royal Enfield Continental GT 535 Single Cylinder (daily) : 1985 Honda CG125 (my first bike) : 2014 AJS Daytona 125 (my mums bike)

[stinkwheel]

[Riejufixing]